My venerable RCRP05B is starting to fail after 7 long years of abuse (kids) and I grabbed myself a Nevo C2 off ebay. One thing I wanted to do was use the actual Roku icons for the soft buttons and I found a way to get them directly from the device using only your web browser!

1) find the IP address of your Roku in Settings -> Network -> About (may slightly differ depending on device, I only have a Roku TV)

And voila! You're given a 290 x 218 transparent PNG of the icon used in the Roku menus, ready to be resized, edited, and loaded into your RMIR file. Do note you have to right click -> save as and change the file type to "All Files", then append ".png" to the end of the file name.